EVALUATION OF DEXMEDETOMIDINE COMBINED WITH
ROPIVACAINE TOXICITY ON SPINAL CORD IN RATS
YING YING, CANGYUAN JIN, WENGUANG HUANG, WEIPING ZHENG *
Department of Anaesthesiology, Taizhou Enze Medical Center (Group) Enze Hospital, No.1 East of Tong Yang Road, Luqiao
District, Taizhou, 318050, Zhejiang Province, China
*corresponding author: zhengweiping8897@126.com
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Abstract:
The aim of this study was to investigate the toxicity of epidural injection of dexmedetomidine combined with ropivacaine on
the spinal cord of rats. Forty-eight Sprague Dawley (SD) rats were randomly divided into four groups: Control group (0.3 mL
0.9% saline solution), Dex group (0.3 mL solution containing 10μg dexmedetomidine), Rop group (0.3 mL solution 0.75%
ropivacaine) and Dex + Rop group (0.3 mL solution containing dexmedetomidine 10 μg + 0.75% ropivacaine). Pain
threshold (PT) was calculated before and at 5, 30, 60, 120 and 240 minutes after epidural injection, respectively.
Furthermore, acute toxicity was assessed 3 days after injection, and chronic toxicity was evaluated at 7 and 21 days after
injection. The toe-clamping test was used to assess motor and sensory impairment. At 3, 7 and 21 days after epidural
injection, spinal cord tissues were collected for pathological observation and to calculate the abnormal rate of neurons. At 3,
7 and 21 days after administration, the toe-clamping reaction and gait of rats in each group were normal. There were no
significant differences in the basic PT values among the groups (p > 0.05). Compared with the control group, the PT values
of Dex group increased significantly at 5, and 30 minutes after administration. Compared with Dex group, PT of Rop group
increased significantly at 5, 30, 60 and 120 minutes after administration (p < 0.05). The PT of Dex + Rop group increased
significantly at 30, 60, 120 and 240 minutes after administration compared with Dex group (p < 0.05). Moreover, PT of Dex
+ Rop group increased at 30, 60, 120 and 240 minutes after administration compared to Rop group (p < 0.05). The abnormal
rate of neurons in Dex + Rop group was higher than that in Dex group and in Rop group at the 3rd and 7th days (p < 0.05),
however, there was no significant difference at the 21st day (p > 0.05). In Dex + Rop group the abnormal rate of neurons in
the 3rd and 7thdays was higher than in the 21st day (p < 0.05), these differences were not observed in other groups (p > 0.05).
No significant injury was observed in spinal cord tissues in Control, Dex and Rop groups at any stage (p > 0.05). In the Dex
+ Rop group, it was observed adhesion and inflammatory cell infiltration in spinal cord tissues in the 3rd and 7th days (p <
0.05). In conclusion, dexmedetomidine administrated alone in epidural space doesn’t produce obvious neurotoxicity, but in
combination with ropivacaine it determines a slight spinal neurotoxicity that is reversible in a short period of time.

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